Optical device for viewing photographic images



c. LANGBERG 'OPTICAL DEVICE FOR VIEWING PHOTOGRAPHIC IMAGES l M'ANolv. 21,` 1944.

Filed Jan. 19, 1942 INVENTOR. Mules Lan'gbelg,

ranma i skt) ,the general public.

' Patented Nov. 21, 1944 AUmrroSTATES PATENT OFFICE y OPTICAL DEVICE FOR VIEWING PHOTOGRAPIIIC IMAGES Y Charles Langberg, New York, N. Y.

Application January 19, 1942, Serial No. 427,270

` l1 Claim;

The present invention relates to an optical device by means of which photographic images and particularly Kodachrome transparencies and the like may bel enlarged and viewed or examined; More particularly still the invention re-V lates to a device of the class described which is so small that it may readily be carried, for example in a mans pocket.

A number of :attempts have been made to con- ,struct devices adapted to the viewing of Kodationed has been the fact that all, or nearly all,

of them required a special light source.

In the past when viewing prints or transparenciesyin a concave mirror, the print or transparency was necessarily held in a position in front of the mirror which resulted when the mirror was held in the observers hand in having the picture or transparency between the ob-A servers body and the mirror. In my device by utilizing two mirrors, it is possible for the print or transparency to be in a position substantially in the plane of the4 one mirror and for the second mirror to occupy the position which formerly was occupied by the transparency. Thus the effective distance of'the image reflected in the first mirror is greatly increased thereby resulting in increase of magnification without corresponding increase of distance between the first mirror and the slide or photoprint and, furthermore, it is possible to use light sources which are independent of the device since, as has been explained, the observers position is not such as to block normal daylight or normal artificial light. A

Ina'ddition the use of concave mirrors is beneflcial since it prevents detrimental chromatic defects and results in producing a relief effect from the Kodachrome or other slides. In fact the impression gained by the observer is that of observing 'a Kodachrome slide of comparatively great size rather than that of observing afmagnfled image this being due to the fact that the vconcave mirrors do not produce glare nor disturbed reflection such as is prevalent on lens surfaces.

The device of my invention -comprises a compact, inexpensive transparency viewer which provides an extremely great enlargement when the size of the instrument is taken into consideration. In general my invention comprises a shallow box-like structure with an aperture therein in which the slide or film transparency to be viewed may be inserted. This box is so constructed that light from any source, as for example daylight, may be utilized. The light passes through the photographic film image and forms an imake of the picture thereon upon a mirror (which may 'be either plane or convex and may form an image either unmagnied or magnified). A second mirror located on the wall of the device in which the aperture above mentioned is also located, reflects the image from the first mirror to a position such that it may be readily observed. The second mirror is a magnifying mirror and it alone or in conjunction with the first mirror, if thatalso is a magnifying mirror, serves to produce a greatly enlarged image of the picture present upon the slide or transparency.

It is thus an object of my invention to produce an optical device for observing film transparencies and the like which shall be inexpensive to manufacture while at the same time capable of producing a high degree of magnification.

It is another object of my invention to produce such a device which may be folded in order that it may be carried even more readily and which may be adjusted to give varying degrees of magnification.

It is another object of my invention to produce a device for observing lm transparencies in which the mirror arrangement above described may be utilized or in the alternative, an objective lens may be used for direct viewing of the illuminated transparency.

I1; is a further object of my invention to produce a. device of the class described in which the mirrors utilized may be of molded rather than of ground glass and yet the distortion normally produced by such mirrors may be corrected.

It is a still further object of my invention to v provide a relief effect and give depth of vision to the image of the picture viewed.

Other objects and features of the invention will appear when the following specification is considered in connection with the appended drawing in which Figure 1 is a vertical cross-section view of one embodiment of my invention, and

vpartly in vertical cross-section of a second form mirror II.

of `my invention, this form including means for `folding. the :box-like structure in order .that it maybe even'more compact than is the structure lofFigure .1.

'Referring now to Figure 1,*there is shown at I .a rectangular box-like structure having a cover 2 hinged to the rearward wall thereof at 3, the cover and Afront wall of the box being provided. with cooperating rlatch members at 4 andla. Near the top of the rear wall of box I there is a concave-mirror 6 which. may be of molded glass (commonly known as a commercial magnifler") .and .which is silvered on its outer face as indicated at 5. Beneath this mirror there is an aper- 'ture of substantially the size of the normal card- Lboard mountingin which Kodachrome transparencies arek supplied tothe public.

l This aper- .ture .has channelmembers on 4the top and two sides thereof so that .it is possible to insert a slide 4into position in the aperture as shown at 8; vFixed permanently within the aperture as indicated at 1 is a ground glass which serves to .diffuse the light prior to its transmission through .the slide from the rear of the device (from thev left as seen in Figure 1). The path of the light `toward the instrument is indicated by the arrow as shown 'by the dotted lines in Figure 1 until it is out of the path of vision from the objective lens 9 which isxed in an aperture in the front wall of the box I and supplied with an eyepiece shown at I0. It will be seen that when desirable lthe slide 8 may be viewed from the eyepiece 'I0 and lens 9, the only magnification in this instance being that brought about by the lens 9.

AWhen the mirror II is lin its lower position, as

shown in Figure 1, an image of the slide B is lformed at adistance X to the right of mirror II equal tothe distance of the slide to the left of This image of the slide will in this instance beof approximately the same size as the original slidebut `it will be obvious .as the description vproceeds that a concave mirror may be utilized whereby the image will be enlarged. Whether enlarged or not, the image,.formed at apoint such as I4, will be reflected into the concave mirror 6 and maybe viewed by an observer along such a line as that indicated at I3, the observers eye being necessarily at a position such-as I2. The amount of magnification will obviously depend to some extent upon the dis- 4tancebetvveen the observers eye and the mirror J6 but this magniflcationvwill always be limited i by the ysizeof the mirror 5. However, if it is desired to .look at only a small portion ofthe `slide thenfit ris possible to keep only that portion within vthe confines of the mirror 6 and consequently to procure a very much greater enlargement of that particular portion than can be procured while the entire photographic likeness is being observed.

.It will be seen that by the use of the two mirrors, it is possible to make the box I much shallower than would be the case if a single mirror were utilized since if this were done the slide itself would necessarily be positioned at I4 wherefore the box would have to be of twice the depth which I employ. In fact the depth of the box in the present device is about 2 Inches and thus it may be carried in a pocket or .the like. Due4 to this combination of mirrors, furthermore, it is unnecessary to utilize a `ilpeoial light sourcealthough this has been necessaryin the past. In devices utilizing a single .mirror (whether magnifying or not) one observing the image in a mirror such as 6 would necessarilybe in such a position as to block with his body all transmission of light through the slide to the mirror when the slide was placed in a position such as I4. In this connection, it may be stated that the box of Figure 1 is somewhat enlarged and that its actual size is 'even-smaller than is shown in the figure. Obviously the box Imay-be used for transportation and storage of slides or other items when not in use as a viewer.

The invention disclosed hereinabove may,of course, be embodied in many forms and a second form thereof is shown by way of example in Figure 2. In this embodiment of the invention a framework comprising side rails I6 and I1 is provided, the rails I6 being longer than rails I1. A member 25 (shown in side elevation) is hinged 0n a pin 24 which extends between side rails I6 at the top thereof so that when the member 25 is rotated clockwise into position its lower edge will abut the upper edge of member 28 so that the entire device may be enclosed. The side rails IIi and I1. are provided with slots I8 in which pins I9, extending outwardly from the upper arms of links 20 of a pantagraph arrangement.`

ride. The lower arms of the links 20 are pivoted at points 2I to the side rails I6 and I1.and the two pantagraph links at each side of the device are pivoted at the central point 22. It will be seen that with this arrangement, the two rails Il and I1 may be moved together so that the instrument may be placed in a very compact form for carrying.

A concave mirror 6 exactly similar to that of Figure l and having a silvered exterior surface 5 likewise similar to that of Figure 1, is mounted in any suitable manner as for example ina backing member such as that shownat 20, this member being in turn mounted on and extending between said rails I8. The member 28 extends downwardly and beneath the mirror 5 has an aperture therein formed with grooved. top and side to receive a slide inserted from the bottom, such a slide being shown In position in'FIgure 2 and indicated by the numeral 8. vAlso extending between the side rails I6 near the bottom thereof is a pair of channels 21 having mounted therein a ground glass 1 exactly similar to that vof Figure 1 and used for the same purpose, i. e., to diffuse the light falling on slide or transparency 8.

Mounted on the forward pair of side rails I1 and extending between them is a mirror 23, the mounting in this instance comprising a plastic or like back 28 against which the mirror is held by means of the annular ring 30 affixed to the backing 28. The mirror 23 is silvered on its rear or right hand surface (Fig. 2) and thus although the forward or left hand surface is plane, the mirror 23 is actually a concave mirror and serves to produce a magnified image of the slide 8. In this connection it should be noted that'a mirror such as that described may be substituted for the mirror I I of Figure 1 or that a plane mirror such as II may replace mirror 23,

In the same manner as has been previously described in connection with Figure 1, light emahating from any source will pass through the rconsequently subject to the production of distortion due to the distortion of their surfaces invariably produced by cooling this is of no importance since when two such mirrors are used they may'be rotated until the distortion produced by one is compensated by the distortion produced by the other. This is always possible due to the fact that the image distortion resulting from the surface distortion produced by cooling is always along one axis only and consequently by placing the distortion axes at right angles to each other the resultant distortion is minimized if not completely eliminated.

` Both devices as shown may be subject to slight amount of Keystone distortion but this may readily be avoided by simply inclining the slide mounting channels at a slight angle to the vertical.

The device of Figure 2 has the advantage of extreme compactness but as shown in Figure 2 is subject to the disadvantage that random light v rays may enter from the sides since the box "structure is not complete. However, this disadvantage may readily be obviated by using bellows extending from front to rear on both sides of the device. In both embodiments of the invention, it will be noted that la cover (2 or 25) is so positioned when the instrument is in use that it serves to prevent random light rays from entering the device from the top and further serves to shade the eyes of the observer from light rays emanating from whatever source may be utilized to illuminate the slide 8.

While I have described preferred embodiments of my invention, it will be apparent that many other forms of the invention might be devised without departing from the spirit or the principle thereof. For this reason the scope of the invention is to be determined solely by the appended claim and not by the foregoing description.

What I claim is:

In a pocket type slide viewer, in combination, a framework comprising two elements spaced apart, pantagraph linkages connecting said elements, a concave magnifying mirror mounted on one element of said framework, a slide receptacle also mounted on said element, substantially in the plane of said mirror, a light diiusing element mounted on said frame element in a line with and behind said slide receptacle, a second concave magnifying mirror mounted in the second element of said framework in a plane substantially parallel to that of the said first mirror, and in alignment with said slide receptacle and diffusing element, said pantagraph linkages serving to make the structure foldable and ser"- ing likewise to make the distance between said` frame elements adjustable whereby the images produced by transmission of light through said diffusing element and slide in said slide receptacle may be variously magnified.

CHARLES LANGrBERG.v 

